Many printed circuit board (PCB) assemblies can be mass produced through automated or semi-automated processes. During production or assembly, a PCB can be populated with electronic components, for example, with through-hole or surface-mount technology, to form the PCB assembly. The electronic components can be attached to the PCB through a variety of soldering techniques. For example, in high volume production, population of the electronic components to the PCB can be performed by a surface-mount placement machine and bulk wave soldering.
There are many situations, however, when skilled technicians manually refinish or repair the electronic PCB assembly, for example, soldering some components using tweezers and a fine tip soldering iron, often with the aid of a microscope. This manual refinish or repair typically occurs during a prototyping stage when components are swapped in a PCB assembly or during a repair process when a manufactured PCB assembly has a defective component and it is more cost-effective to have expert personnel manually remove and replace the defective component using appropriate equipment. This manual refinishing or repair of PCB assemblies is often called rework. Properly carried out, rework can restore functionality of the PCB assembly without significantly affecting its subsequent lifetime.
As sizes and conductor pitch of components to be installed on a printed circuit board have shrunk, the precision of manual placement of those components onto the printed circuit board has increased. Since rework is typically performed manually by expert personnel, the use of highly accurate vision-alignment systems with high resolution and magnification has become ubiquitous. Many soldering rework stations in lab environment utilize optical microscopes during rework of these PCB assemblies. While optical microscopes can provide rework technicians a quality view of the PCB assembly, they are typically difficult to properly calibrate. For example, since microscopes typically only allow a view to a small location on the PCB assembly, for example, just a component or two on the PCB assembly, the calibration of the PCB assembly can include locating the component to perform rework, and then iteratively positioning and focusing the optical microscope until the optical microscope provides a view of the located component.
To help combat the limitations of the optical microscope, some soldering rework stations have replaced optical microscopes with video inspection systems, for example, including a camera to capture a two-dimensional image of the PCB assembly and a monitor to display the captured image. While the electronic inspection systems can allow for a larger view of the PCB assembly as compared to the optical microscope, the two-dimensional image makes performing the rework difficult, due to the lack of depth-perception in the two-dimensional image. Further, since rework often includes soldering, the lack of depth-perception can cause inadvertent contact to the PCB assembly by a soldering iron or a soldering gun, which, due to intense heat, can damage a PCB board or other components in the PCB assembly.